Biomedical subjects

P Avan

Publications and source records attributed to P Avan.

At least 55 records · Page 3Linked to original sources

PubMed1995

[Deafness in the neonatal period: basis for screening].

Deafness must be recognized in infancy in order to reduce auditory disability to a minimum. To achieve this, it is important to implement screening programmes as soon after birth as possible. In the United States, the Joint Committee on Infant Hearing recommended in 1982 that identification of hearing loss should be screened in the neonatal period. This early detection is now considered critical for optimal rehabilitative outcome. This paper presents the "state of art" neonatal screening principles and procedures. In France, neonatal screening programs for auditory dysfunction are not consistent with these principles. Evoked otoacoustic emissions represent an important advance in screening for hearing loss in normal neonates and babies from neonatal intensive care units. This method records very low intensity sound energy released by the cochlea in response to a brief sound stimulation. These otoacoustic emissions show promise as a rapid, cost-effective means of quickly discharging all babies with normal peripherical auditory systems.

Deafness↗

PubMed1995

Transient-evoked otoacoustic emissions and high-frequency acoustic trauma in the guinea pig.

Transient-evoked otoacoustic emissions (TEOE) disappear when hearing loss exceeds 40 dB in the range 1-4 kHz, due to impairment of cochlear outer hair cells. Early screening of sensorineural hearing losses is based on this finding. However, little is known as to the frequency specificity of TEOE abnormalities in a damaged cochlea. TEOE were recorded in 18 normally hearing guinea pigs in a range from 1.5 to 5 kHz before and after exposure to loud pure tones (3-10 kHz, 95-105 dB SPL, 1-10 min). The thresholds of eighth-nerve compound action potentials (CAP) were monitored with a round-window electrode; it was confirmed that acoustic overexposure resulted in typical high-frequency threshold elevations (10 to 50 dB). Most TEOE components were found at lower frequencies at which CAP thresholds did not change. However, a significant linear regression was found between their amplitudes and the percentage of basal cochlea with unaltered CAP thresholds (r = 0.69, p < 0.0001). Two alternative hypotheses are proposed to account for this correlation. Either acoustic trauma induced some minute cochlear damage at places tuned to low frequencies and TEOE were more sensitive to it than CAP thresholds, or significant contributions to lower-frequency TEOE came from the most damaged cochlear places tuned to much higher frequencies.

Acoustic Stimulation↗

PubMed1995

[Definition of normal criteria of provoked otoacoustic emission in the newborn infant].

Evoked otoacoustic emissions (EOE) were recorded with ILO88 in a group of 254 neonates (n = 508 ears) in order to determine the normative data. In this study, it was found that: (i) the mean EOE amplitude was 20.2 dB SPL, (ii) the EOE amplitude of the right ear was significantly higher than those of the left ear, (iii) the mean time necessary to record EOE in both ears was around three minutes, and (iv) EOE spectrum was large (mean = 638-5,611 Hertz). These data permit to precise the clinical interest of EOE for screening auditory function in neonates.

Hearing Disorders↗

PubMed1994

On the shape of (evoked) otoacoustic emission spectra.

In a preceding paper [Wit et al., (1994) Hear. Res. 73, 141-147] it was shown that realistic time-frequency plots for click evoked otoacoustic emissions can be synthesized by adding a large number of gammatones. It is necessary in such a synthesis to make the inner ear frequency to place map, from which the central frequencies of the gammatones are taken, slightly irregular along the entire cochlear partition. The present paper shows that this approach leads, in a rather straightforward way, to (quasi-) periodicity in synthesized spectra of evoked otoacoustic emissions. These spectra show good resemblance with spectra from real ear emission measurements.

Acoustic Stimulation↗

PubMed1994

Wavelet analysis of real ear and synthesized click evoked otoacoustic emissions.

Wavelet analysis was performed to obtain time-frequency analyses of click evoked otoacoustic emissions from normal ears and one ear with a high-frequency hearing loss; mainly to introduce this relatively new method and to show its potentials for emission analysis. The same analysis was then used to obtain time-frequency decompositions of synthesized emissions. It was found that the introduction of a slightly irregular frequency to place relation for the inner ear yielded synthetic results that were remarkably similar to those obtained from real ears.

Acoustic Stimulation↗

PubMed1994

Auditory threshold evaluation by distortion-product oto-acoustic emissions using decision support system.

Distortion-product oto-acoustic emissions (DPOEs) were measured in 102 normal-hearing and hearing-impaired ears to examine the sensibility, specificity, positive predictive value and negative predictive value of this test in a real clinical setting using two decision support systems. The first model only considered the presence or the absence of DPOEs in response to a 52 dB SPL stimulation intensity. The second model used two consecutive tests: i) the presence or the absence of DPOEs in response to a 52 dB SPL stimulation intensity, and ii) evaluation of the slope of each DPOE input-output function. The sensitivity of these two models varied between 1 and 0.83 whereas the specificity varied between 0.95 and 0.72 as a function of the frequency tested. The first model proved to be a very sensitive test, but the introduction of a second criterion of decision (i.e., the slope of DPOE input-output function) did not enhance the validity of the test.

Acoustic Stimulation↗

PubMed1994

[Role of the basal cochlea in the genesis of evoked acoustic oto-emissions in the subject with normal hearing].

The aim of this study was to determine the role of the basal part of the cochlea (8-16 kHz) on the genesis of evoked otoacoustic emissions (EOEs) in normally hearing subjects (0.25-8 kHz thresholds below or equal to 20 dBHL). This study was realized on 43 subjects. The EOEs were generated by a linear click of 0 dB (ILO88 Ref.). The high-frequency (8-16 kHz) audiometric thresholds varied between 30 and 74 dBHL while conventional audiometric thresholds were below 20 dBHL. Correlation studies between EOE amplitude and audiometric thresholds were statistically significant only when the high frequency thresholds were considered. Those data are a new argument for the hypothesis that EOEs are generated by the global cochlear activity.

Adult↗

PubMed1994

[Effect of a hearing aid on progressive hearing loss].

A group of 72 children with hearing aids followed in 4 different clinical settings presented progressive increase in sensorineural hearing loss. The mean hearing loss over time, the duration of hearing aid use and the gain were studied to test the hypothesis that continued progression in hearing loss was due to overly powerful amplification. No correlation was found between the progressive increased gain levels were associated with less progression in hearing loss than at lower gain levels. Therefore, the use of hearing aids was not directly and significantly related to the increase in hearing loss in the population studied. However according to the above criteria a few cases (4%) of progressive hearing loss did seem to be associated with hearing aid use.

Acoustic Stimulation↗

PubMed1993

Temporal patterns of transient-evoked otoacoustic emissions in normal and impaired cochleae.

The spatial distribution of outer hair cells that participate in generating transient-EOE frequency-components has been investigated in man. According to several models (e.g. Wilson (1990) Hear. Res. 2, 527-532; Zwicker (1986) J. Acoust. Soc. Am. 80, 154-162; Wilson and Kemp (Eds.), Cochlear Mechanisms, Structures, Functions and Models, Plenum Press, NY), EOEs result from interferences between broadly distributed contributions, responsible for their long frequency-dependent delay. This work presents an analysis of the temporal patterns of click- and tone-burst-EOEs in human ears when contributions to EOEs are reduced by noise-induced lesions with audiometric notches centred around 4 kHz (N = 46). Although the auditory thresholds at the frequencies of the studied EOE-components were always normal, these components exhibited drastic and predictable changes compared to normal control ears (N = 40). (1) Their temporal pattern at the highest EOE frequency fmax just below the audiometric notch appeared to be determined by the cochlear state at high frequencies (6 to 8 kHz). Either it was normal and the EOE exhibited a complicated beat-structure, or it was impaired and the time envelope of the EOE was simple. In contrast, any type of time pattern could be observed in normal ears. (2) The temporal patterns of EOEs one octave below fmax always presented many beats and short delays. The proposed interpretation is that contributions to a transient-EOE component at frequency f can come from distant basal cochlear areas, i.e. more than 1 and sometimes 1.5 octaves from the place tuned to f. Therefore, the possible relationships between transient-EOEs and tuning mechanisms which presumably involve only a small number of OHC need further investigations.

Acoustic Stimulation↗

PubMed1993

Exploration of cochlear function by otoacoustic emissions: relationship to pure-tone audiometry.

The amplitudes, growth functions and detection thresholds of evoked otoacoustic emissions (EOE) were measured in 44 normally hearing subjects and 138 patients with two categories of cochlear dysfunctions: (a) acoustic trauma; and (b) presbycusis. Separate sets of experiments were also performed: (a) detection of stimulus frequency emissions; and (b) click EOE. EOE properties were studied around 2 kHz, 1 kHz and 0.75 kHz (+/- 0.1 kHz). A partial correlation and multivariate analysis was carried out to investigate the relationships between EOE properties and puretone auditory thresholds (from 0.25 to 8 kHz, half-octave steps). For each experiment and each frequency, only one highly significant correlation was found, linearly relating the n kHz EOE threshold with the hearing threshold at 2n kHz: there was a shift of about one octave between EOE amplitudes and audiometric data. This means that EOE thresholds give no direct information about the local cochlear state. A simplified model has been implemented, which assumes that EOE thresholds and amplitudes are proportional to the total number of residual active sites along the organ of Corti, i.e., to the total length of active basilar membrane towards the base of the cochlea. It is shown that this model accounts for the results revealed by the statistical analysis and closely fits the experimental data.

Acoustic Stimulation↗

PubMed1993

Audiological assessment of eleven congenital hypothyroid infants before and after treatment.

Eleven congenital hypothyroid newborns were consecutively referred for audiological evaluation before any treatment. Evoked otoacoustic emissions were present bilaterally in 9 newborns. These results suggest the normality outer hair cells and contrast with results obtained in experimental studies. The auditory brainstem responses in 6 newborns showed a prolonged wave I, as previously reported by other authors. At 9 to 12 months of age, all children treated had evoked otoacoustic emissions in at least one ear. In 9 cases, the auditory threshold was normal (equal to or below 20 dB) as determined by behavioural tests.

Auditory Threshold↗

PubMed1993

Frequency specificity of human distortion product otoacoustic emissions.

The amplitudes and growth functions of distortion product otoacoustic emissions (DPOE) at 2f1-f2, elicited by two primary tones f1 and f2 with a constant frequency ratio f2/f1 = 1.23 and varying geometric mean values 1, 1.5, 2, 4, 6 and 8 kHz, were measured for 25 normal subjects and 50 patients with sensorineural hearing loss. Partial correlations between DPOE amplitudes and auditory thresholds (0.25 to 8 kHz, half-octave steps) were examined. The amplitude of DPOE evoked by low-intensity primary tones (at or below 62 dB SPL) was strongly correlated only with the auditory threshold at their mean frequency, and DPOE disappeared for local hearing losses larger than about 30 dB. Moreover, DPOE amplitudes did not depend on the basal cochlear state. Confounding effects of middle ear transmission and aging were not significant in this set of experiments. When elicited by higher intensities of primary tones (72 dB SPL), DPOE exhibited a more complex and non-local behavior, and their sensitivity to hearing loss decreased. These results suggest that when low-intensity primaries are used, DPOE patterns provide frequency-specific information on the local cochlear state.

Acoustic Stimulation↗

PubMed1993

[Screening of deafness in the young child. Value, techniques and initial results of products of acoustic distortion].

Distortion-product otoacoustic emissions are otoacoustic emissions evoked by two pure tones called primaries and proposed in order to provide a frequency specific investigation of the cochlea. This paper first reports complete input-output functions of distortion-product otoacoustic emissions for conventional audiometric frequencies in a population of 35 neonates without any risk for cochlear function. Distortion-product otoacoustic emissions could be useful, in association with evoked otoacoustic emissions and comportemental audiometry, to precisely evaluate the peripheral auditory system in infants and neonates.

Audiometry↗

PubMed1992

Distortion-product otoacoustic emissions. Values for clinical use.

Distortion-product otoacoustic emissions are otoacoustic emissions evoked by two pure tones. They are proposed as a frequency-specific test of the mechanical properties of the cochlea. The aim of this study was to measure distortion-product otoacoustic emissions in a clinical setting to establish the most interesting values suitable for clinical use and the clinical interest of the method. The statistical analysis of the data points out some clinically interesting values: (1) a screening limit value of 30 dB hearing level and when measuring distortion-product otoacoustic emissions in response to 52 dB sound pressure level for studying active frequency selective mechanisms; (2) a screening limit value of 50 dB hearing level and when measuring distortion-product otoacoustic emissions in response to 72 dB sound pressure level for studying passive cochlear mechanisms; and (3) the slope of the input-output function. All physiologic properties of the cochlea fit with these basic distortion-product otoacoustic emission properties. These criteria can be used whatever the population studied and the material used for distortion-product otoacoustic emissions recordings. Distortion-product otoacoustic emissions can be used as a screening test to separate (1) subjects with normal hearing and subjects with a hearing threshold above 30 dB hearing level (distortion-product otoacoustic emissions in response to a 52 dB sound pressure level "primaries" [ie, pure tones] stimulation intensity), and (2) patients with a hearing threshold above or below 50 dB hearing level (distortion-product otoacoustic emissions in response to a 72 dB sound pressure level primary stimulation intensity). Distortion-product otoacoustic emissions cannot be used as a more precise audiometric test.

Adolescent↗

PubMed1992

Hypothetical roles of middle ear muscles in the guinea-pig.

The attenuation of incoming sounds induced by acoustic reflex triggering was evaluated from the cochlear microphonic response to test tones in 45 awake guinea-pigs. Although control electromyographic measurements proved that the stapedius muscle was contracting, neither impedance changes nor attenuation induced by contralateral reflex-eliciting sounds were detectable in 30 cases out of 45. For ipsi- and bilateral stimulations, an attenuation was detectable for 7 guinea-pigs out of 10. In the guinea-pigs for which a reflex-induced change was found on CM, the mean attenuation was weak i.e. of the order of 2 dB at 20 dB above reflex threshold. These results were quite different from those obtained during control experiments in the rabbit for which CM attenuation was much larger. However, large attenuations associated with middle ear muscle contractions were found in the guinea-pig in other circumstances, i.e. during self-vocalization or when spontaneous muscle contractions occurred during anaesthesia. It is concluded that middle ear muscles can have several different functions, and that even when it exists, attenuation of loud sounds might not be their primary role.

Acoustic Impedance Tests↗

PubMed1992

Analysis of possible interactions of an attentional task with cochlear micromechanics.

Several contradictory studies have been published regarding the effect of selective attention on cochlear mechanics, possibly modulated through efferent pathways. Click-evoked otoacoustic emissions have been proposed as a highly sensitive tool for testing the hypothesis of such a modulation. In this study, two other types of evoked otoacoustic emissions (i.e. distortion products and stimulus frequency emissions between 1 and 4 kHz) were measured on 20 normal subjects in absence and presence of a visual selective attention task. The duration of measurements at a given frequency was short enough to eliminate possible artefacts due to long-time averaging. No significant change was observed in these signals, considered as probes of cochlear micromechanics. It is concluded that in this set of experimental conditions, selective attention has a negligible effect on peripheral sensitivity.

Acoustics↗

PubMed1992

Spontaneous and evoked otoacoustic emissions in preterm neonates.

Spontaneous (SOEs) and evoked otoacoustic emissions (EOEs) were recorded in a group of preterm neonates (N = 134 ears) in order to study the basic properties of SOEs and EOEs as a function of gestational age. In the study, it was found that: 1. EOEs were recorded in 93% of the tested ears; 2. SOEs were recorded in 61% of the tested ears; 3. there were no statistically significant variations of EOE amplitude with gestational age; 4. EOE spectrum did not vary with age; and 5. the two main factors influencing EOE amplitude were the SOE presence and the fast Fourier transform spectrum, especially the lower limit of the spectrum. Thus, the maturation of outer hair cell properties appears to be complete at 32 weeks of gestational age. Because a number of infants at risk for hearing loss are preterm babies, screening for EOEs, an objective, rapid, and nontraumatic technique, may prove useful in evaluating peripheral auditory dysfunction in preterm neonates.

Cochlea↗

PubMed1992

Distortion-product otoacoustic emissions in neonates: normative data.

Distortion-product otoacoustic emissions (DPOEs) are otoacoustic emissions evoked by two pure tones and used in order to provide a frequency specific assessment of the mechanical properties of the cochlea. This paper first reports complete input-output DPOE functions for audiometric frequencies between 867 Hertz and 8 kHz in a normal neonate population (normative data). DPOE results were analyzed as a function of evoked otoacoustic emission (EOE) properties. Neonates having normal EOEs have large DPOEs. DPOE amplitudes in neonates are larger than in adults. Neonates with atypical EOE frequency spectrum without low frequency components had normal DPOE input-output functions only for high frequencies (above 2 kHz). DPOEs could be useful, in association with EOEs, to precisely evaluate the auditory peripheral function in neonates.

Humans↗